1. Ground-Floors

Impervious ground-floors resting on the solid ground have certain advantages over the ordinary joisted and boarded floors raised a foot or so above the ground or ground-layer. They are more secure against rot, and afford no space for dirt and vermin to lodge, besides effecting, in many cases, a saving in excavation, foundations, and walls.

They may be formed of concrete on the top of the asphalt layer, as shown in figs. 34, 38, and 39, and in Plate II. This concrete need not be more than l or 2 inches thick, save in those exceptional cases where considerable pressure of water has to be resisted. In places where appearance is no object, or where the traffic is light, the concrete may consist of one part of Portland cement and two parts of pea-gravel, well mixed and trowelled or floated to a smooth surface. The less sand that is used the better, as it renders the concrete less durable, and therefore causes more dust. For better work, hard limestone, marble, granite, syenite, spar, alabaster, glass, pottery, etc., crushed and passed through a screen with half-inch meshes, may be used instead of gravel. A mixture of these materials gives variety to the appearance of the floor, and sometimes additional variety is given by pressing somewhat larger pieces into the concrete here and there as soon as it is laid. When the cement has set properly, the floor is ground down with stone rubbers, sand, and water, until a clean polished surface is obtained. Frequently colouring matter - Venetian red, ultramarine, etc. - is added in mixing the ingredients, but a more permanent colour effect is obtained by the use of coloured aggregates, chiefly marble and granite; borders and centres are often finished in different colours. These polished concrete floors are often known as concrete mosaic, but the more general name now is terrazzo. When properly laid, they are extremely durable and dean, and have a pleasing appearance. They are suitable for corridors, pantries, Ac, and also for sculleries, water-closets, bath-rooms, wash-kitchens, and other places where much water is used, but for living-rooms they have the demerit of coldness concrete mosaic must not be confounded with Roman mosaic, each tessera of which is carefully laid by hand in the exact position required by the design. This is a more expensive kind of floor, but affords scope for ornamental effects impossible in the other. The cubes arc usually of marble or fine pottery, the latter being known as ceramic mosaic and the former as marble mosaic. A bed of cement-mortar floated to a perfectly level surface must be prepared to receive the mosaic

Tiles of various kinds arc also used for floor-surfaces, and must be laid in quick-setting cement on a level bed of cement-mortar. Sometimes thin slabs of marble, or of other hard and ornamental stones, are laid in patterns in cement-mortar. All these floors arc as a rule clean and durable, but are often noisy and slippery, and cold.

Sometimes an ordinary smooth finishing coat of cement-mortar is given to the concrete, and on it kamptulicon, linoleum, or cork carpet is glued. These add to the warmth, comfort, and quiet of the room, and are durable enough if the floor be dry. It La best to select a material of one colour throughout, as such a one is most serviceable, and as a rule most pleasing.

For living-rooms, however, a wood surface is usually preferred on account of its warmth. This can be obtained by using either wood-block flooring, or parquetry. The latter is as a rule the more ornamental and perfect flooring.

The ordinary wood-block flooring consists of blocks of wood from 1 to 2 or even 3 inches thick, and usually 9 inches by 3 inches on the face, grooved along the sides as shown in Fig. 86, and laid in molten pitch or bituminous composition on a perfectly level and dry surface of cement-mortar or natural asphalt. The pitch should be well squeezed into the grooves of the blocks, and the whole of the floor when laid should be well planed, so as to bring all the blocks to one smooth and uniform surface. The pitch in which the blocks are embedded is itself damp-proof, but it not infrequently happens that cracks and holes are left in it. through which moisture rises to the wood, causing decay. For perfect safety the ground-layer should be covered entirely with an asphalt damp-course as already described, on which the wood-blocks may be laid in molten pitch in the usual way. Blocks with faulty grooves, or badly laid, or of unseasoned wood (especially pitch-piue), frequently wear loose. Hence special systems of flooring have been devised, in which the blocks are firmly secured to each other or to the bed by means of tenons, dowels, screws, etc These systems undoubtedly have their advantages, and should be adopted where the additional outlay can be afforded.

Fig. 86 Ordinary Wood block Floor.

Fig. 86-Ordinary Wood block Floor.

Various kinds of wood may be used for block floors, the cheapest being yellow or red deal; other woods are pitch-pine, oak, teak, walnut, jarrah, mahogany, and also beech, lurch, and the dark-red Indian wood known as padouk. Red-deal blocks ought never to be less than 1 inch thick; sometimes blocks 2 inches and more in thickness are used. The harder woods are usually laid in Mocks 1 inch or 1 inch thick, the thicker being the more secure and durable, and of course more expensive. The peculiar odour of teak must not be forgotten when the selection of wood is being made; the odour - or rather the oil which yields the odour - apparently renders the wood less liable to the attacks of insects, hut it is to many persons objectionable, and teak cannot therefore always be adopted. Oak is the wood most largely used in good work, walnut, mahogany, etc, being occasionally introduced in bands and patterns to add to the effect.

Hardwood floors are often wax-polished, and sometimes French-polished; these processes add to the brightness of the floors, and at the same time render them cleaner, as all the joints and pores are stopped by the wax and shellac.